Hydrocarbons at the Geochemical Barrier the Northern Dvina–the White Sea

Aliphatic and polycyclic aromatic hydrocarbons have been studied in suspended matter and bottom sediments at the geochemical barrier the Northern Dvina–Dvina Bay during spring flood and low-water season. The increase in the concentrations during spring flood (for aliphatic hydrocarbons, on the average, 154 µg/L) compared with those during low-water season (on the average, 52 µg/L) has been shown to be short-time. The losses of hydrocarbons at this geochemical barrier are governed by variations of water salinity, river flow, and lunar phases and can reach 96% (August 2017). The composition of alkanes and polycyclic aromatic hydrocarbons in river water mostly showed the predominance of petroleum components. In the course of sedimentation and as salinity increases, petroleum hydrocarbons decompose, making their effect beyond the gravitational part of the marginal filter of the Northern Dvina minor. The effect of redox processes in the sediment stratum on hydrocarbon distributions is stronger than that on Corg.